Cagayan Valley (Lambak ng Cagayan 
in Filipino; Tana' nak Cagayan in the Ibanag Language; Tanap ti Cagayan in the Ilocano Language) is a region of the Philippines, also designated as Region II or Region 02. It is composed of five provinces, namely: Batanes, Cagayan, Isabela, Nueva Vizcaya, and Quirino. It has three cities; Cauayan City, its regional center-Tuguegarao, and its commercial center-Santiago City.
Most of the region lies in a large valley in northeastern Luzon, between the Cordilleras and the Sierra Madre mountain ranges. The Cagayan River, the country's longest river runs through its center and flows out to Luzon Strait in the north, in the town of Aparri, Cagayan. The Babuyan and Batanes island groups that lie in the Luzon Strait also belong to the region.